(i) Field of the Invention
The present invention relates to a photosensitive polyimide precursor composition. More specifically, it relates to a photosensitive polyimide precursor composition which has little volume shrinkage at the time of curing and which is excellent in adhesion to substrates and shelf stability.
(ii) Description of the Related Art
As heat-resistant photosensitive materials, photosensitive polyimides have been widely used to form insulating films and passivation films for semiconductors. Most of the photosensitive polyimides are mixtures of compounds having polymerizable carbon-carbon double bonds and polyimide precursors, and products of the compounds and the precursors obtained by a chemical bond such as an ester bond. For example, such photosensitive polyimides are known from Japanese Patent Laid-open Nos. (Sho) 54-145794 and (Hei) 2-144539, and Japanese Patent Publication No.(Sho) 55-41422. However, in order to practically carry out a pattern treatment, it is necessary to introduce a large amount, e.g., 50% or more of a compound having a carbon-carbon double bond to the polyimide precursor, and therefore the deterioration of resolving properties and large volume shrinkage at the time of curing cannot be avoided. On the other hand, to avoid such a problem a method has also been suggested in which a compound capable of generating an acid by light irradiation is utilized without using the compound having the carbon-carbon double bond. For example, the compound capable of generating an acid by light irradiation is blended with a polyimide having an acyloxy group in Japanese Patent Laid-open No. (Hei) 3-763, or a polyamic acid derivative having an organic group introduced by an ester bond in Japanese Patent Laid-open No. (Hei) 4-120171, whereby the pattern treatment is possible. In the former, however, the volume shrinkage can be controlled, but the adhesion to substrates is inferior. In the latter, the resolution is excellent, but the preparation of the polyamic acid derivative is inconveniently intricate.